Use of Residual Herbicides for Tough to Control Weeds in Snap Beans Final Report for 2012

Use of Residual Herbicides for Tough to Control Weeds in Snap Beans Final Report for 2012 Submitted to Pennsylvania Vegetable Marketing and Research Program c/o William Troxell, Executive Secretary 815 Middle Road Richfield, PA 17086-9205 Submitted by: Mark VanGessel University of Delaware Research and Extension Center 16483 County Seat Highway Georgetown, DE 19947 Ph: 302-856-2585 ext 510 Fax: 302-856-1845 Email: mjv@udel.edu Dwight D. Lingenfelter Penn State Dept. of Plant Science 116 Ag Sciences & Industries Bldg. University Park, PA 16802 Ph: 814-865-2242 Fax: 814-863-7043 Email: DXL18@psu.edu

Introduction: Snap beans are produced on approximately 7,000 acres in Pennsylvania and 3,000 acres in Delaware (PDA Ag Statistics, 2009-10; DE Agricultural Statistics). Weed control can be a problem in this very important processing and fresh market crop. Weed control impacts snap bean yield as well as harvest efficiency, harboring other pests, and reducing the deposition of other pesticides. Only a limited number of herbicides are currently available for snap beans. Balancing herbicide selection to provide residual weed control throughout the growing season, but not limiting rotations can be challenging. Some herbicides such as the Raptor, Pursuit, Sandea, and Reflex have replant restrictions that can impact their use. Furthermore, there have been documented herbicide-resistant weed biotypes to some of these herbicides in our region. Other herbicides such as Basagran have little to no impact on crop rotations but Basagran has a very limited number of weed species that it controls. Furthermore, certain weeds such as common lambsquarters and common ragweed can sometime be difficult to control especially if they escape soilapplied herbicides or in dry weather situations. Research in the Mid-Atlantic region has demonstrated that when certain herbicides are used in certain combinations they tend to complement each other quite well (i.e. Reflex plus Basagran). A number of issues for herbicide usage in the Mid-Atlantic region need additional work to determine the consistency of results, and obtain data over a wider range of environmental and production conditions. We proposed to continue the evaluation of weed control programs in snap beans, building upon previous trials. This project has two main emphasizes, to determine the most efficient use of residual herbicides (use at planting [] versus postemergence []), and evaluating herbicide combinations and surfactants for difficult to control weeds in snap beans, particularly lambsquarters. Reflex and Sandea are labeled for both and application and we evaluated which approach provided the most benefit for this region. In addition, we evaluated two residual herbicides for their potential use in snap beans (Sharpen and Zidua). Secondly, we evaluated Basagran, Reflex, Sandea, and Raptor applied postemergence () at different use rates and in tank-mix combinations. The inclusion of certain adjuvants (e.g., surfactants) was also evaluated to determine if any provide improved postemergence herbicide performance with minimal crop injury. The studies were conducted at the Penn State research farm in Centre County and at the University of Delaware, Georgetown research farm. The purpose of conducting research at multiple locations over more than one growing season, is to evaluate these herbicide programs under different growing and climatic conditions, including different soil types, broader range of weed species, and irrigated and non-irrigated conditions. Benefits to Pennsylvania snap bean growers include updated information in vegetable production guides and other educational resources on how to more efficiently control weeds, especially troublesome broadleaf weeds, with greater rotational flexibility, improved resistance management, and with existing products. Objectives: 1. Determine the most efficient use of residual herbicides (use at planting [] versus postemergence []); 2. Evaluate herbicide combinations and surfactants for difficult to control weeds in snap beans, particularly lambsquarters. 3. Determine the effect of these herbicide treatments on snap bean stand, injury, and yield. Methodology: Experiments were conducted at two locations: the Russell E. Larson Agricultural Research Farm in Centre County and at the University of Delaware Research and Extension Center in Sussex County in 2012. The

original protocol was modified and split into evaluation of preemergence () herbicides and a second trial evaluating postemergence () herbicides. The core treatments were the same at both locations, but additional treatments were included to adjust for local practices. The preemergence study evaluated preemergence control of annual weeds in a stand of snap beans (Tables 1 and 3). The studies were planted and sprayed on June 29 at PSU and July 5 at UD. Preemergence treatments were applied immediately after planting. The postemergence study at PSU was conducted in a fallow setting with a dense population of several weed species (Table 2). The postemergence trial at UD was treated with Magnum at 1.25 pts at planting and treatments were applied July 19, when weeds averaged 4 inches tall and the snap beans were 1 st to 2 nd trifoliate stage. The treatments were evaluated in a randomized complete block design with three replications. The plots were 10 feet wide by 25 feet long, and Slenderpack was planted at PSU and Dart was planted at UD. Plots were not cultivated. Crop injury and/or weed control was evaluated routinely, and yield was collected on September 4 at PSU and August 23 at UD Results & Discussion Rock Springs: (Tables 1 & 2): Site is a silt loam soil ph 6.7, and 2.2 % organic matter In the preemergence study, all treatments provided 82-94% control of giant foxtail. All treatments, except for + Sandea or Reflex, provided 90% or greater control of lambsquarters. Aside from + Sandea, all treatments provided 90% or greater control of redroot pigweed. Treatments that contained Zidua initially caused 5-6% injury to snap beans but did not cause any yield reduction. Yields ranged from 5.6 to 8.8 tons/a. However, there was a trend toward better yields in all of the plots that had a herbicide treatment compared to the untreated check. In the postemergence study, none of the treatments provided >80% control of all the of weed species. Treatment of Basagran + Sandea + Raptor + NIS was the most consistent and provided 79 to 93% control of the weeds. Sandea + Raptor + NIS also provided adequate control (79 to 89%) of the species. The Basagran (3 pt) + Raptor + COC + UAN also provided more consistent control of the species, however the higher rate of Basagran and the addition of the hotter adjuvants would likely cause too much injury/burning to snap bean. (This is a program that is labeled for use in soybeans.) For best results apply herbicide to weeds they are small (i.e. < 6-8 inches tall). However, when controlling larger weeds be sure to include the appropriate herbicide for the weeds present. In this trial, lambsquarters control was best with Raptor; common ragweed control was best with Sandea or Reflex; pigweed control was best with include Sandea or Raptor; and Basagran provided the smartweed control. Size of the weed at application time matters. For example, the lambsquarter population ranged from 2 to 20 tall. Because of this, control varied from 50 to 65% control of lambsquarters >15 tall and 80-90% lambsquarters control if they were 12 or less at application. Spray coverage also was an issue. In areas were the weeds were dense and tall, control was reduced. In general, there was no significant difference on weed control between the adjuvants that were included in the spray mixture.

Results & Discussion UD REC: (Tables 3 & 4): Site was a loamy sand, ph 6.0, and 1.3% organic matter In the soil-applied study Sharpen reduced snap bean stands by 90%, not a viable option for snap beans on coarse-textured soils Zidua caused stunting that was visible until pod formation The site received irrigation immediately after preemergence application which increased injury in this trial, particularly with Sandea. In situations where irrigation or significant rainfall occurs within a day or two of application, stunting is often observed. Sandea was safer when applied as a postemergence herbicide in this trial. Yields were highest with and Reflex applied at planting or Reflex applied postemergence and followed by Sandea. Sandea as preemergence application resulted in lower yields than when it was applied postemergence. Zidua treatments had the lowest yields in the trial. Pigweed weed control was not different among the treatments, ranging from 86 to 100% control. There was little difference among treatments for morningglory control (Sharpen provided 82% control but injury was not acceptable). Sandea, either preemergence or postemergence provided the highest level of control, but was only 71 to 75% control. The higher rate of Magnum (1.67 pts compared to 1.25 pts) did not differ from the lower rate, so there was no benefit to the additional 0.5 pt of Magnum in this trial. In the postemergence study crop injury did not differ with surfactant selection with Raptor plus Basagran, but the addition of 30% UAN increased injury with Basagran plus Reflex. As in the preemergence study, Sandea applied postemergence was safer than preemergence applications. At 2 week after treatment, herbicides applied with LI-700 had less injury than either NIS alone or NIS plus UAN, but no differences were observed 4 weeks after treatment. All treatments provided excellent control of common lambsquarters and pigweed species. Morningglory control was best with Raptor plus Basagran plus NIS plus UAN and the three-way combination of Reflex, Basagran, plus Raptor. Yields were similar for all treatments in this trial. Hot weather forced a split set of snap beans that severely impacted yield. Two-year Summary: Snap bean injury: More snap bean injury was observed in DE than at PSU for both years. Although the addition of 30% UAN increased injury with Basagran plus Reflex at UD in 2012, this was not observed at the other sites or years. Adjuvants at both locations did not increase the amount of crop injury, nor did they a significant impact on weed control Some of the preemergence herbicides had more injury at UD as well. Sharpen resulted in unacceptable snap bean injury, and Zidua caused stunting that was visible until pod formation; and both reduced yields. In situations where irrigation or significant rainfall occurs within a day or two of application, stunting from Sandea is often observed. Sandea was safer when applied as a postemergence herbicide. Weed control: Overall lack of consistency in weed control results from site to site and year to year.

Pigweed weed control generally did not differ among the treatments, ranging from 84 to 100% control. Sandea and Reflex were much more effective for common lambsquarters control when applied as application rather than All other treatments were over 93% control in DE, whereas only plus Reflex as a treatment was rated over 90% control at PSU. Morningglory was only present at the UD location, and in 2012, control was best with Raptor plus Basagran plus NIS plus UAN and the three-way combination of Reflex, Basagran, plus Raptor (over 80% control); and in addition Basagran plus Reflex performed well in 2011. Table 1. Effect of herbicides on weed control, crop injury, and yield in snap bean at Centre Co., PA, 2012. Late-season ratings are presented*. Snap bean variety is Slenderpack. Herbicide(s) Rate/A Giant foxtail Lambsquarters Pigweed Slenderpack Injury (%) Slenderpack Yield (Ton/A) Untreated - 0 0 0 0 5.6 Magnum 1.67 pt 82 82 84 1 7.0 + Sandea + 0.67 oz Magnum 1.67 pt 89 85 91 1 7.9 + Reflex + 1.25 pt Magnum 1.67 pt 92 90 89 2 8.2 + Sharpen + 1 fl oz Zidua 2 oz 90 91 95 3 8.9 + Reflex + 1.25 pt Zidua 2 oz 82 88 90 3 8.0 + Sandea + 0.67 oz Magnum 1.67 pt 92 96 96 1 7.2 + Lorox + 1.3 lb Magnum 1.67 pt 94 94 97 1 6.8 + Reflex + Pursuit + 1.25 pt + fl oz LSD (P=.05) 14 10 12 2 3.6 * Late season ratings taken 9/4/2012; snap beans harvested 9/4/2012

Table 2. Effect of snap bean herbicides on large broadleaf weed control at Centre Co., PA, 2012*. No crop was planted Herbicides* (adjuvant) Rate/A Lambsquarters Common ragweed Redroot pigweed Smartweed Untreated - 0 0 0 0 Reflex 1 pt 39 77 79 76 Sandea 0.67 oz 10 88 80 74 Sandea + Reflex 0.67 + 1 pt 38 82 83 84 Sandea + Raptor 0.67 + 4 fl oz 80 89 86 79 Basagran + Sandea + Raptor pt + 0.67 oz + 4 fl oz 79 88 88 93 Basagran + Raptor pt + 4 fl oz 74 72 86 93 (NIS + UAN) 2 qt/a Basagran + Raptor pt + 4 fl oz 77 65 86 92 Basagran + Raptor pt + 4 fl oz 71 62 84 94 (LI 700) 4pt/100gal Basagran + Reflex pt + 0.75 pt 56 88 69 95 (NIS + UAN) 2 qt/a Basagran + Reflex pt + 0.75 pt 43 85 74 93 Basagran + Reflex pt + 0.75 pt 55 90 80 93 (LI 700) 4pt/100gal Basagran + Raptor + Reflex pt + 4 fl oz + 0.75 pt 66 87 87 94 Basagran + Raptor 3 pt + 4 fl oz 81 79 86 96 (COC + UAN) 1 qt/a 1 gal/a LSD (P=.05) 16 13 9 6 * Late season ratings taken 7/19/2012

Table 3. Effect of herbicides on crop injury, weed control, and yield at University of Delaware s Research and Education Center, Georgetown, DE*. Snap bean variety is Dart. Snap Snap Snap Pigweed Mornglry Snap Bean Bean Bean Species Species Bean Stunting Stunting Stunting Control Control Yield Applic. % % % % % lbs / A Herbicide(s) Rate/A timing July 17 July 31 Aug 13 Aug 13 Aug 13 Aug 23 Untreated - 0 0 0 0 0 N/A + Sharpen 1.25 pt + 1 fl oz 96.3 a 90 a 91.7 a 86 81.7 a N/A + Reflex Zidua + Reflex 1.25 pt + 1.25 pt 2 oz wt + 1.25 pt 7 d 5.7 d 3.3 cd 95 60 c 5065 ab 23.3 b 28.3 b 15.7 b 100 69.3 bc 3373 c fb Reflex + NIS 1.25 pt fb 1 pt 9 d 15 c 9 bc 90 61.7 c 5111 ab + Sandea 1.25 pt + 0.67 oz wt 18.3 c 26.7 b 9 bc 96 71 abc 4173 bc fb Sandea + NIS 1.25 pt fb 0.67 oz wt 0 e 2.3 d 0 d 100 75 ab 6617 a + Reflex 1.67 pt + 1.25 pt 10.7 d 9.7 cd 0 d 100 63.3 c 5083 ab LSD (P=.05) 4.16 7.34 7.42 10.5 13 1593 Treatment Prob (F) 0.0001 0.0001 0.0001 0.0748 0.0143 0.019 *Treatments in each column followed by the same letter are not significantly different.

Table 4. Effect of postemergence () herbicides on crop injury, weed control, and yield at University of Delaware s Research and Education Center, Georgetown, DE*. Snap bean variety is Dart. Snap Snap Snap Mornglry Snap Bean Bean Bean Species Bean Stunt Stunt Stunt Control yield Herbicide(s) Applic. % % % % lbs / A Adjuvant(s) Rate / A timing July 28 Aug 1 Aug 13 Aug 13 Aug 23 Untreated 0 0 0 0 4243 a Basagran + Raptor pt + 4 fl oz 10.7 d 9.7 cde 5.7 87 a 4377 a NIS+ 30% UAN % + 2 qt Basagran + Raptor pt + 4 fl oz 9 d 9.7 cde 3.3 75 bcd 5451 a NIS % Basagran + Raptor pt + 4 fl oz 13 cd 4.7 ef 4 78 abc 5804 a LI-700 % Basagran + Reflex pt + 0.75 pt 18.3 ab 15 bc 2.3 72 cd 4494 a NIS+ 30% UAN % + 2 qt Basagran + Reflex pt + 0.75 pt 11.3 d 10.7 bcd 2.3 75 bcd 5850 a NIS % Basagran + Reflex pt + 0.75 pt 13.3 bcd 0 f 2.3 68 d 5209 a LI-700 % Basagran + Raptor pt + 4 fl oz 11.3 d 9 de 3.3 82 ab 5037 a + 0.75 pt NIS % + Reflex 1.25 pt + 1.25 pt 17.3 bc 15.7 ab 5.7 76 bcd 4912 a Sandea + NIS 0.67 + % + Sandea 1.25 pt + 0.7 oz wt 23.3 a 20.7 a 11.7 79 abc 4372 a Reflex + NIS 1 pt + % LSD (P=.05) 5.14 5.54 7.1 9 1831 Treatment Prob(F) 0.0004 0.0001 0.2062 0.0216 0.5119 *Treatments in each column followed by the same letter are not significantly different. Entire site was treated with Magnum at 1.25 pt/a # treatments made to 4 tall weeds (snap beans were 1 st to 2 nd trifoliate stage)

Pictures from the postemergence study at Rock Springs. Photo taken a few days after application End of season Untreated check End of season Sandea + Raptor + NIS Photo taken a couple weeks after application End of season Sandea + NIS treatment End of season Basagran + Sandea + Raptor + NIS

Addendum: 2011 Data. Snap bean trials for management of troublesome weed species at PSU s Russell E. Larson Agricultural Research Farm in Centre County and the University of Delaware Research and Extension Center in Sussex County in 2011. Magnum rates in DE were 1.25 pts/a and 1.67 pts/a at PSU due to sandier soil type (loamy sand versus silt loam). =preemergence applications made at planting; POT=postemergence applications at 3 to 4 weeks after planting; WAT=weeks after treatment. Treatments followed by the same letter are not significantly different from one another. Activity PSU UD Variety Slenderpack Dart Planting date June 3, 2011 June 15, 2011 applications June 3, 2011 June 15, 2011 applications July 6, 2011 July 7, 2011 Yields August 1, 2011 August 1. 2011 PSU Centre County UD Sussex County Snap bean Lambsqrtr Velvetleaf Snap bean Snap bean Lambsqrtr Morningglory Snap bean 21-Jul 1-Aug 1-Aug 1-Aug 22-Jul 1-Aug 1-Aug 1-Aug % Control Control Yield % Control Control Yield Treatment Rate Applic Injury % % (lb/a) Injury % % (lb/a) Name Rate (/A) Timing 2 WAT 4 WAT 4 WAT 2 WAT 4 WAT 4 WAT Untreated 0 d 0 d 0 b 1442 ab 0 e 0 c 0 c n/a 1.67 Pt 1 cd 90 a 57 a 2255 ab 3.3 cde 100 a 44 b 487 a 3 cd 60 bc 55 a 1977 ab 1.7 de 70 b 69 a 1020 a fb Reflex +Sandea fb Sandea fb Sandea 1 0.67 oz/a 0.67 oz/a 1.25 0.67 oz/a 3 bcd 85 ab 60 a 1884 ab 9.6 abc 100 a 67 ab 364 a 6 bcd 52 c 80 a 2092 ab 0 e 0 c 44 b 856 a 5 bcd 77 abc 81 a 3045 a 11.7 ab 100 a 76 a 821 a

fb Sandea +LI 700 +Sandea fb Reflex +Raptor +UAN +Raptor +Raptor +LI 700 +UAN +LI 700 1.25 0.67 0.5 0.67 1 4 4 4 0.5 0.75 0.75 0.75 0.5 oz/a oz/a fl oz/a fl oz/a fl oz/a 7 bc 73 abc 84 a 2149 ab 14 a 100 a 83 a 487 a 4 bcd 81 ab 65 a 2827 a 14 a 100 a 90 a 470 a 7 bc 73 abc 78 a 1561 ab 13.3 a 97 a 86 a 866 a 5 bcd 72 abc 70 a 2565 ab 4.7 b-e 100 a 70 a 917 a 6 bcd 72 abc 60 a 2284 ab 8 a-d 100 a 78 a 929 a 10 b 75 abc 70 a 1903 ab 13.3 a 97 a 85 a 710 a 4 bcd 73 abc 70 a 3499 a 11.7 ab 100 a 84 a 657 a 7 bc 77 abc 71 a 1993 ab 9 abc 93 a 74 a 720 a formulation was Magnum and rate at PSU was 1.67 and 1.25 for UD.